A testing procedure for predicting strength in artificially cemented soft soils

Consoli, Nilo César; Winter, Daniel; Rilho, Andry Soares; Festugato, Lucas; Teixeira, Bruno dos Santos

doi:10.1016/j.enggeo.2015.06.005

Cited by 31 publications

(8 citation statements)

References 19 publications

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“…The effect on soil of using lime and cement has been regarded as very similar in many respects (Al-Rawas et al 2005), although cement-treated soils seem to have the least impact on the environment because of less chemical leaching, and they can provide greater sustainable strength for longer periods (Muhunthan and Sariosseiri 2008;Puppala et al 2015). The strength properties of Portland cement (PC)-treated soils have been studied by several authors (Consoli et al 2015;Caraşca 2016). Chen et al (2016) examined the variation in strength of marine clay treated with cement during a wet deep mixing work at the Marina Bay Financial Centre in Singapore and found that the strength of the improved clay varied from 0.7 MPa to about 5 MPa.…”

Section: Introductionmentioning

confidence: 99%

Swell and microstructural characteristics of high-plasticity clay blended with cement

Abbey

Eyo

Ngambi

2019

Bull Eng Geol Environ

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This study presents the effect of high plasticity on swell potential, swelling pressure and micro-structural characteristics of kaolinite-bentonite mixed clays. Five different mix ratios of kaolinite bentonite mixture of 100:0, 90:10, 75:25, 50:50 and 25:75 in % by weight of dry kaolinite were used. All five synthesised soils were then mixed with 0%, 5% and 8% of cement by weight of dry soil, cured for 28 days and subjected to the Atterberg limit, one-dimensional oedometer and scanning electron microscope test. The inclusion of 5% and 8% cement reduces the plasticity index of the treated soils as the percentage of bentonite increases. The effects on plasticity of treatment with 5% and 8% cement after a 28-day curing period was evaluated, and the results show that reduction in plasticity index resulted in decreased swell potential and swelling pressure of the kaolinitebentonite mixed clays. The results of microstructural analysis of 5% cement-treated soils show formation of flocculated fabric and cementation of soil particles, and filling with cementitious compounds of the voids of flocculated fabric in the soil. The reduction in swell can be attributed to the resulting compacted and dense mass of treated soils due to cementation of soil particles and cation exchange. The complex swell behaviour of high-plasticity kaolinite-bentonite mix is explained using the onedimensional oedometer test, by further experimental study and examination of the microstructure of treated soils.

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Section: Introductionmentioning

confidence: 99%

Swell and microstructural characteristics of high-plasticity clay blended with cement

Abbey

Eyo

Ngambi

2019

Bull Eng Geol Environ

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“…Unconfined compressive strength (UCS) is one of the most important parameters in the design of cut-off walls for prevention of seepage in water-retaining walls. The UCS of portland cement (PC) stabilized soils are usually high, making PC the most commonly used binder in soil improvement, (Holm 2003;Terashi 2003;Consoli et al 2015;Oana 2016). Chen et al (2016) examined the variation in the UCS of marine clay improved with cement during a wet deep mixing work at the Marina Bay Financial Centre in Singapore.…”

Section: Introductionmentioning

confidence: 99%

Development of Strength Models for Prediction of Unconfined Compressive Strength of Cement/Byproduct Material Improved Soils

Abbey

Ngambi

Ganjian

2017

Geotechnical Testing Journal

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This paper presents the possible inclusion of pulverized fuel ash (PFA) and ground granulated blast slag (GGBS) in cement deep soil mixing for enhancement of unconfined compressive strength (UCS) of weak soil materials for construction purposes. The main focus of this paper was to investigate the UCS of cement-, cement/PFA-and cement/PFA/GGBS-improved soils, and development of mathematical and graphical models for prediction of UCS for use in design and construction. Samples of cement, blends of cement and PFA, and cement/PFA/GGBS were prepared using 5 %, 10 %, 15 %, and 20 % by weight of dry soil and tested for UCS after 7, 14, 28, and 56 days. A multiple regression analysis was conducted using the SPSS computer program. The results showed that soil materials with lower plasticity show higher strength development compared to those of higher plasticity for cement improvement. The study has also revealed that the inclusion of PFA and GGBS can cause a reduction in the amount of cement in deep soil mixing, which can result to reduced cost and emission of carbon dioxide (CO 2) during construction. The developed mathematical and graphical models could give reliable predictions of UCS for weak soil materials with initial UCS less than or equal to 25 kPa and for water to binder ratio of unity based on the observed agreement between experimental and predicted data. The developed multiple regression models have also been validated using different mixtures of 6 %, 8 %, 12 %, and 16 % of binders.

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“…e water content of the clay on the site was 35%-62%, the clay mineral content was 22%-40%, and the saturated density was 1.89-1.93 g/cm 3 . e clay was in a fluid or plastic state, the color ranged from gray to dark gray, and the clay was moderately to highly compressible.…”

Section: Soft Clay Specimensmentioning

confidence: 97%

“…To improve the clay's engineering properties and allow it to be used as a resource, different strengthening and solidifying methods are now employed such as mixing the clay with cement, lime, gypsum, or fly ash. ese materials are used because they are easily available and inexpensive [2][3][4][5][6][7], but the effect of these admixtures on the clay's engineering properties is in some cases not ideal. e effects are constrained by the type and quantity of stabilizer material used, the moisture content of the soft clay, weathering condition, curing condition, and curing time, among other factors [8].…”

Section: Introductionmentioning

confidence: 99%

Microbial‐Induced Carbonate Precipitation for Strengthening Soft Clay

Xiao

Wei

Cai

et al. 2020

Advances in Materials Science and Engineering

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Currently, calcite produced in sediments by microbial-induced carbonate precipitation (MICP) is mainly used as a strengthening binder in sand because sands are porous and have good permeability. Conventional wisdom does not consider MICP to be suitable for use in soft clay because of the clay particles’ small size and its minimal porosity. Because of the clay’s high water content and complex chemical composition, very little research has been done and not much is known about the use of MICP in soft clay for strength enhancement. For this paper, soft clay specimens were prepared by mixing a solution containing Sporosarcina pasteurii bacteria, solutions with different concentrations of nutrient salts, and soft clay. Unconfined compressive strength tests were carried out on these specimens after they had cured for 28 days in a moisture-controlled environment. These laboratory tests were used to study the chemical reactions, the clay’s strength, and other influencing factors. The results are as follows: (1) directly mixing a S. pasteurii solution, nutrient salts, and soft clay considerably improves the uniformity of the spatial distribution of the bacteria and the nutrients in the soft clay. Directly mixing these constituents promotes the formation of calcium carbonate and greatly simplifies soft clay sample preparation. (2) It is feasible to use MICP to increase the strength of soft clay. Compared to control specimens cured under the same conditions but without introduced nutrients and bacteria solution, the unconfined compressive strength of MICP-treated specimens can be increased by as much as 2.42 times to an unconfined compressive strength of 43.31 kPa. The water content in MICP-treated specimens was significantly reduced by the MICP reactions and in one case decreased from 40% to 30.73%. (3) The strength enhancement of microbially solidified soft clay is the result of two processes: urea hydration catalyzed by enzymes consumes water in the clay and the bacterially precipitated calcite forms in the sediment’s pores. (4) The micro-organism-produced calcite in the soft clay increases the calcite abundance from 0% to as much as 3.5%. (5) The MICP-treated strength of soft clay varies with the concentration of the nutrients provided. For the experimental conditions used for this paper, the optimum concentration of the CaCl2·2H2O and CH4N2O nutrients is 0.5 mol/L.

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A testing procedure for predicting strength in artificially cemented soft soils

Cited by 31 publications

References 19 publications

Swell and microstructural characteristics of high-plasticity clay blended with cement

Swell and microstructural characteristics of high-plasticity clay blended with cement

Development of Strength Models for Prediction of Unconfined Compressive Strength of Cement/Byproduct Material Improved Soils

Microbial‐Induced Carbonate Precipitation for Strengthening Soft Clay

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